A runestone of power is a small chip of polished stone etched with a rune.

Traditionally, this rune is one of many runes for magic, but more recently created runestones of power often substitute runes from other cultures—the nature of the rune itself has no effect on the runestone’s actual powers. These objects are potent aids to all spellcasters who cast spells spontaneously (bards, inquisitors, oracles, sorcerers, and summoners, but not to spellcasters like clerics who have the option to spontaneously cast certain spells).

Once per day, a spontaneous caster can draw upon a runestone of power to cast a spell—doing so is part of the spellcasting action, and expends that runestone’s power for the day rather than one of the spellcaster’s actual spell slots for the day. An expended runestone of power recharges its capacity after 24 hours. The spell must be of a particular level, depending on the runestone.